What is a KVM Switch?

The KVM switch received its name from its function. The KVM switch is a switch allowing one keyboard, video monitor and mouse to be used on more than one computer without physically reconnecting them. This is a great advantage in a situation where two or more computers must be used in limited space, or where multiple servers are used occasionally without the need for an individual workstation for each machine.

Use

In the example of the smallest switch, the keyboard, mouse and video monitor are connected to one side of the switch and at least two computers are connected to the other. When one computer is needed, a button or switch is used to transfer to that computer. When done, the worker switches back the same way. You can manage two totally separate workstations this way without moving from desk to desk.

Types

KVM switches come in a variety of sizes and types to fit your needs. A small one may only have interfaces for two computers where a larger one may connect to six or more computers. The type of interface also needs to match the computer. Older models had PS2 and VGA connections. Newer models use USB and VGA connections. It is important to match the type of interface to the type of computer you are using.

Mechanical switches

The original KVM switches were just modified data switches that used sets of mechanical contacts to switch from one computer to another. This is simple and cheap; during regular operation this switch works fine, but has drawbacks. When computers are first turned on and connected to a KVM switch, there may be trouble. Many computers are set to stop and report an error if they do not see a mouse or keyboard at boot time, and a mechanical switch totally disconnects the computer not currently in use from these devices.

Electrical Switches

This type of switch is the solution to the problem mentioned above. An electrical switch is sometimes called an active switch because it actively sends back a message to all the computers connected to it that there are mice keyboards and video monitors connected to them. This allows all the computers to be turned on at once and they will report no boot time errors.

Non-Physical Alternatives

There are a variety of different software suites that perform the same function as a KVM switch over a network. These allow you to log into the computer remotely and control it as if your keyboard, mouse and video monitor were directly connected to the computer you use on the network. Some of these use remote desktop protocols and others use their own software clients installed on the target computer to perform the same function.

References

• KVM Switch: Webopedia
• KVM Switch: Chris Pirillo.com